Physiological plant disorder
Diagnosis of disorders
Diagnosis of the cause of a physiological disorder (or disease) can be difficult, but there are many web-based guides that may assist with this. Examples are: Abiotic plant disorders: Symptoms, signs and solutions;[1] Georgia Corn Diagnostic Guide;[2] Diagnosing Plant Problems (Kentucky);[3] and Diagnosing Plant Problems (Virginia).[4]
Some general tips to diagnosing plant disorders:
- Examine where symptoms first appear on a plant—on new leaves, old leaves or all over?
- Note the pattern of any discolouration or yellowing—is it all over, between the veins or around the edges? If only the veins are yellow, deficiency is probably not involved.
- Note general patterns rather than looking at individual plants—are the symptoms distributed throughout a group of plants of the same type growing together? In the case of a deficiency all of the plants should be similarly effected, although distribution will depend on past treatments applied to the soil.
- Soil analysis, such as determining pH, can help to confirm the presence of physiological disorders.
- Considering recent conditions, such as heavy rains, dry spells, frosts, etc., may also help to determine the cause of plant disorders.
Weather damage
Frost and cold are major causes of crop damage to tender plants, although hardy plants can also suffer if new growth is exposed to a hard frost following a period of warm weather. Symptoms will often appear overnight, affecting many types of plants. Leaves and stems may turn black, and buds and flowers may be discoloured, and frosted blooms may not produce fruit. Many annual plants, or plants grown in frost free areas, can suffer from damage when the air temperature drops below 40 degrees Fahrenheit (4 degrees Celsius). Tropical plants may begin to experience cold damage when the temperature is 42 to 48 °F (5 to 9 °C), symptoms include wilting of the top of the stems and/or leaves, and blackening or softening of the plant tissue.
Frost or cold damage can be avoided by ensuring that tender plants are properly hardened before planting, and that they are not planted too early in the season, before the risk of frost has passed. Avoid planting susceptible plants in frost pockets, or where they will receive early morning sun. Protect young buds and bloom with horticultural fleece if frost is forecast. Cold, drying easterly winds can also severely inhibit spring growth even without an actual frost, thus adequate shelter or the use of windbreaks is important.
Drought can cause plants to suffer from water stress and wilt. Adequate irrigation is required during prolonged hot, dry periods. Rather than shallow daily watering, during a drought water should be directed towards the roots, ensuring that the soil is thoroughly soaked two or three times a week. Mulches also help preserve soil moisture and keep roots cool.
Heavy rains, particularly after prolonged dry periods, can also cause roots to split, onion saddleback (splitting at the base), tomatoes split and potatoes to become deformed or hollow. Using mulches or adding organic matter such as leaf mold, compost or well rotted manure to the soil will help to act as a 'buffer' between sudden changes in conditions. Water-logging can occur on poorly drained soils, particularly following heavy rains. Plants can become yellow and stunted, and will tend to be more prone to drought and diseases. Improving drainage will help to alleviate this problem.
Hail can cause damage to soft skinned fruits, and may also allow
Plants affected by
Nutrient deficiencies
Poor growth and a variety of disorders such as leaf discolouration (
Nutrient (or mineral) deficiencies include:
- Boron deficiency
- Calcium deficiency
- Iron deficiency
- Magnesium deficiency
- Manganese deficiency
- Molybdenum deficiency
- Nitrogen deficiency
- Phosphorus deficiency
- Potassium deficiency
- Zinc deficiency
References
- ^ a b Schutzki, R.E.; Cregg, B. (2007). "Abiotic plant disorders: Symptoms, signs and solutions. A diagnostic guide to problem solving" (PDF). Michigan State University Department of Horticulture. Michigan State University. Archived from the original (PDF) on 24 September 2015. Retrieved 10 April 2015.
- ^ Lee, R.D. (2012). "Georgia Corn Diagnostic Guide". extension.uga.edu. University of Georgia Cooperative Extension. Retrieved 10 April 2015.
- ^ Green, J.L.; Maloy, O.; Capizzi, J.; Hartman, J.; Townsend, L. (2011). "Diagnosing Plant Problems: Kentucky Master Gardener Manual Chapter 7" (PDF). www2.ca.uky.edu. Kentucky Cooperative Extension. Retrieved 10 April 2015.
- ^ Niemiera, A.X. (2009). "Diagnosing Plant Problems". pubs.ext.vt.edu. Virginia Cooperative Extension. Retrieved 10 April 2015.
- ^ ISBN 079237150X.
- ^ "Improved fallows". teca.fao.org. FAO. Archived from the original on 13 November 2017. Retrieved 10 April 2015.
Improved fallow is also land resting from cultivation but the vegetation comprises planted and managed species of leguminous trees, shrubs and herbaceous cover crops. These cover crops rapidly replenish soil fertility in one or at most two growing seasons. They shorten the time required to restore soil fertility; they help to improve farmland productivity because the plant vegetation that follows them is superior in quality; and they increase the range of outputs, because the woody fallow species can also produce fuel wood and stakes.